def brute_force_root_finder(f, a, b, n):
    from numpy import linspace
    x = linspace(a, b, n)
    y = f(x)
    roots = []
    for i in range(n-1):
        if y[i]*y[i+1] < 0:
            root = x[i] - (x[i+1] - x[i])/(y[i+1] - y[i])*y[i]
            roots.append(root)
        elif y[i] == 0:      
            root = x[i]
            roots.append(root)
    return roots

def demo():
    from numpy import exp, cos
    roots = brute_force_root_finder(
        lambda x: exp(-x**2)*cos(4*x), 0, 4, 1001)
    if roots:
        print(roots)
    else:
        print('Could not find any roots')

if __name__ == '__main__':
    demo()
